The Long Term Evolution Advanced standard, also known as LTE Advanced, LTE-Advanced or LTE-A, is a mobile communication standard adopted by the 3rd Generation Partnership Project (3GPP) as a major enhancement of the LTE standard. In an LTE-Advanced system, carrier aggregation technology is used to improve the system's peak rates and support broadband communication up to 100 MHz, so as to ensure that users can transmit data through multiple component carriers and at the same time maintain good compatibility with systems based on the LTE standard.
In a cellular mobile communication system, when a user moves from a first area covered by a cell A associated with a first base station to a second area covered by a cell B associated with a second base station, cell switching (also known as “handover” or “handoff”) is required to ensure the strength of the signal received by the user is maintained above a minimum acceptable level. Conventional cell switching strategies, which determine when cell switching occurs for a given user, are generally based on the received power and set a switching threshold slightly higher than the minimum acceptable signal strength. This way, the conventional strategies ensure that the cell switching is completed before the weakened signal interrupts the communication while unnecessary switching is avoided.
However, there is an issue with the conventional cell switching strategies as the basis for judging whether a user switches from one cell to another at a given point in time is the strength of the signal received by the user. In the context of carrier aggregation, path loss, shadow fading and a small scale of facing on the different component carriers are different for the various component carriers utilized based on the LTE-Advanced standard. This leads to significant differences among the signal strengths of different component carriers. Consequently, cell switching based on the total signal strength received by the user according to conventional cell switching strategies would be impractical if not impossible when carrier aggregation is implemented.